In IP telephony systems, a cable telephony adapter (CTA) device is used to allow a user to send and receive information in secure transactions over an IP telephony network. In typical operation, a series of signaling messages are exchanged that register the CTA device with the IP telephony network before a secure channel with another user can be established.
Therefore, there is a need to authenticate the CTA device. The authentication provides protocol security and allows the IP telephony network to authenticate the identity of the CTA device. The CTA should be authenticated from the very beginning of the provisioning process. Otherwise the provisioning process would be open to additional denial of service attacks—since some provisioning exchanges can be forged. In addition, it is desirable for the service provider to cryptographically identify the CTA device—to make sure that only authorized devices are allowed in its IP Telephony network. If only the subscriber—but not the CTA device itself—were authenticated, this would not be possible.